A refinement of the crystal structure of KSCN
A refinement of the crystal structure of KSCN
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DOI：
10.1107/s0567740868003808
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发表时间：
1968-08
期刊：
影响因子：
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通讯作者：
C. Akers;S. W. Peterson;R. Willett
中科院分区：
文献类型：
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作者：
C. Akers;S. W. Peterson;R. Willett
以前已经对硫氰酸钾的晶体结构进行了两次研究(Klug，1933；Bfasem，Gtinther&Tubin，1934)。这两项研究都利用了地带性数据，仅在碳原子在硫氰酸盐离子中的位置上有很大不同。由于投影数据的结果存在固有误差，以及出于理论目的对更准确的原子间距离的需求日益增长，因此决定重新研究这种结构。分析级晶体从乙醇-水溶液中重结晶。两个独立的晶体，其尺寸从0.07到0-10毫米不等，用于收集数据，因为第一个在调查完成之前就开始分解。系统灭绝(k=2n+L的OKL和L=2n+1的HOL)与Pbcm以前的空间群归属一致。由进动照片确定的晶格常数为a=6.673+0.003，b=6.715+0-003，c=7.543+0.005。强度数据是在配有通用电气单晶定向器的Picker衍射仪上采集的。角度设置是用现有的Fortran II程序计算的(Shoemaker，1962)。对Lorentz偏振进行了修正，但忽略了吸收效应。三维傅立叶合成(Sly，Shoemaker&Van den Hende，1962)，基于从先前的一项研究(Klug，1933)的位置计算出的符号，给出了碳原子的正确位置，并改进了其他位置。用Bing，Martin&Levy(1962)程序进行各向异性最小二乘精化，最终得到RI=0.080和R3=0.067。散射因子是从《国际X射线结晶学表格》(1962)中获得的。表1列出了最终参数，表2给出了观测和计算的结构系数。使用的加权方案如下：
Two previous investigations of the crystal structure of potassium thiocyanate have been made (Klug, 1933; Bfissem, Gtinther & Tubin, 1934). Both studies made use of zonal data and differed substantially in only the position of the carbon atom in the thiocyanate ion. Because of the inherent errors in results from projection data and the growing need for more accurate interatomic distances for theoretical purposes, it was decided to reinvestigate this structure. Crystals of analytical grade were recrystallized from an alcohol-water solution. Two separate crystals, whose dimensions varied from 0.07 to 0-10 mm, were used to collect the data because the first began to decompose before the investigation was complete. Systematic extinctions (Okl for k = 2 n + l and hOl for l = 2 n + 1) agree with the previous space group assignments of Pbcm. Lattice constants, determined from precession photographs, are a = 6.673 + 0.003, b = 6.715 + 0-003, c= 7.543 + 0.005 A. Intensity data were collected on a Picker diffractometer equipped with a General Electric single-crystal orienter using Mo Ka radiation. Angle settings were calculated with an existing Fortran II program (Shoemaker, 1962). The Lorentz-polarization corrections were made but absorption effects were neglected. A three-dimensional Fourier synthesis (Sly, Shoemaker & Van den Hende, 1962), based on signs calculated from the positions of one of the previous investigations (Klug, 1933), gave the correct position for the carbon atom and improved the other positions. Anisotropic least-square refinement was carried out with the Busing, Martin & Levy (1962) program, and final values of RI =0.080 and R3=0.067 were obtained. Scattering factors were obtained from International Tables for X-ray Crystallography (1962). Final parameters are listed in Table 1, with observed and calculated structure factors given in Table 2. The weighting scheme used is as follows: